1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine and laser printer and an image forming method.
2. Description of the Related Art
An image forming apparatus such as a copying machine and laser printer generally feeds and conveys recording paper from a paper feeder to an image forming section, carries out image formation by a transfer method (indirect method) or direct method, and ejects the recording paper passing through the image formation to the paper output section. Among such image forming apparatuses, there are those which automatically perform image formation on both sides of the recording paper in response to a duplex printing instruction of the recording paper, and output the recording paper passing through the image formation.
Such an image forming apparatus that carries out the image formation on both sides of the recording paper is disclosed in Japanese patent application Laid-open No. 10-31394 (1998), for example. According to it, if the size of the paper being conveyed through the machine does not agree with the user-designated paper size, and hence the image formation is not carried out normally on the recording paper, the recording paper is ejected to the paper output section without reversing the paper at a reversing section.
According to the patent document, however, if the size of the paper being conveyed through the machine does not agree with the user-designated paper size, the following problems can occur during the printing. More specifically, since the recording paper that is waiting for the back side printing on the conveying path in the reversing section (that is, the recording paper that can be printed normally) is also ejected to the outside, reprinting must be made for all the number of papers being carried through the machine at the same time, thereby increasing a waste of the recording paper. As for the recording paper waiting for the back side printing on the conveying path in the reversing section, such control is also possible that ejects to the outside only the sheet on which the image formation is not made normally first, and then ejects, if the image formation is possible, the recording paper passing through the image formation. In this case, the sheet on which the image formation is made normally is laid on the sheet on which the image formation is not made normally in the paper output section. Thus, the user must search for the sheet on which the image formation is not made normally to remove it, which will result in an increase in the burden of the user.